Field of the Invention
This invention relates to a process for the production of a synthetic crude oil product, having a composition similar to that of natural crudes. From a feedstock of (1) heavy oil, tar sand bitumen or oil shale kerogens, or heavy residuals from these, (2) crushed coal, and (3) coal volatiles that have been pyrolyzed from coal, a blended synthetic crude oil product having benzenoid, paraffinic, napthenic and sulphur components in proportions similar to that found in natural crudes is produced.
The invented process is an integrated one in which crushed coal is thermally pyrolyzed to recover volatiles from the coal, and the coal volatiles, together with crushed coal and a heavy residual material produced, for example, by distillation of heavy oil, are combined and upgraded Preferably the upgraded product is then blended with light ends, for example, those produced by the distillation of heavy oil. The residual remaining after pyrolyzation of the coals and the residual remaining after upgrading are gasified to produce the thermal energy for pyrolyzation, upgrading and to facilitate hydrogen production for upgrading. The coal volatiles exiting the pyrolysis stage are condensed from the hot synthesis gas (syngas) and the syngas once stripped of the coal volatiles is then utilized to produce thermal energy to in turn produce other forms of energy required for the processing and upgrading of the coal--coal volatile--heavy residual mixture. Depending upon the proportions of any constituent in the coal--coal volatile--heavy residual feedstock, the amounts of thermal energy used for any particular energy production can be altered. The process is one incorporating a high degree of integration of the units of the process and of energy production and use, and results in a system which once initiated can be essentially energy self-sufficient in that substantially all of the energy required for processing and upgrading can be economically provided from low value hydrocarbon residuals produced in the process. In addition, energy production within the process can be adjusted to effectively co-process electricity as a significant by-product.
The invention also relates to a pyrolyzation apparatus for pyrolyzing coal to produce coal volatiles in which crushed coal is systematically passed countercurrent to a hot syngas in a vertical tower.
By the utilization of a coal-oil feedstock mixture of preferred proportions, a synthetic light crude oil can be produced comparable to natural light crudes and compatible with the refining capabilities of existing conventional refineries.
The world's higher quality light natural crude oils are those having an API of 35.degree. to 45.degree. with a sulphur content less than 0.5 percent. These high quality light natural crudes cost the least to refine into a variety of highest value end products including petrochemicals and therefore command a price premium. More important, however, world refinery capacity is geared to a high proportion of light natural crude oils with an API of about 38.degree. or higher.
It is generally accepted that world supplies of light crude oils recoverable by the conventional means of drilling wells into reservoirs and the use of nature's pressure, or by pumping to recover the oil, will be diminished to the extent that in the coming decades these supplies will no longer be capable of meeting the world demand.
To find relief from oil supply shortage it will be necessary to substantially increase processing the vast world reserves of coal and viscous oil, bitumens in tar sands and kerogens in oil shale. This source of crude oil remains largely unexploited today although recovery of oil from tar sands is in practice in Canada. In Canadian Pat. No. 1,065,780 I have described an integrated process for the recovery of oil and bitumen from less conventional sources of oil and the upgrading thereof. Canadian Pat. No. 1,065,780, deals with the recovery of oil and bitumen from heavy oil deposits, from tar sands, from shale or from the liquefication of coals and the upgrading of this oil or bitumen in an integrated recovery and upgrading process.
The development of technology for the production of synthetic oil as an alternative to the light crude oil found in nature continues to be plagued by the large capital investments required in recovery and production facilities and a long wait for return on investment. In addition, large expenditures are required to retrofit refineries for synthetic oils recovered from heavy oils and bitumens. In addition, present synthetic oil plants for processing heavy oils, or bitumens from tar sands, have focused more on the development of systems for recovery and production than on energy efficiency, maximization of yield and high environmental processing standards. Except for South Africa's Sasol process, which benefits from low cost labour used in coal mining, straight coal liquefication is not yet cost competitive with synthetic oil produced from tar sands bitumen or heavy oils.
It is of considerable importance that ways are found to produce light synthetic crudes comparable in quality to the rapidly depleting reserves of light natural crudes available from conventional sources and at a cost at least approaching these crudes and fully competitive with the crudes being recovered at higher cost from under the sea or from frontier areas such as the extreme north with its rigorous climate. It is also important that light synthetic crudes are comprised in desired proportions of a mixture of benzenoid, naphthenic and paraffinic components as these three families of compounds comprise essential feedstck to refinery capacity producing today's transportation fuels and feedstocks for the petrochemical industry.
The invented process is designed to enable the economic production of synthetic crude oil having characteristics comparable to the world's best light natural crudes, i.e. an API of 40.degree. or higher, a sulphur content of less than 0.5 percent and balanced proportions of benzenoid, napthenic and paraffinic compounds suitably matched to general refinery market demand and capacity. In the invented process, it has been found that coal which is the most abundant of all fossil hydrocarbons can play a key role in achieving this objective. The benzenoid content of the coal is a factor to the benzenoid content of the final product and contributes synergistically to the hydrogen upgrading.
With the advent of improved methods of recovering heavy viscous oil and tar sands bitumens by in situ methods from many smaller deposits, the development of communal recovery and upgrading systems based on gathering and pipelining relatively small amounts of heavy oil materials to central refineries for synthetic oil production, is strongly indicated. Since large quantities of coal are used in the invented process and large reserves of strip mineable coal are to be found throughout the world it is anticipated that most synthetic oil refineries might very well be sited at the source of coal with heavy oils and/or bitumens being gathered and pipelined to coal. However, raw material supply logistics may dictate that coal would move to synthetic oil refineries located at the sites of large reserves of heavy oil or tar sands bitumens, in some cases. Pipeline systems may evolve in which coal slurries are moved to sites of heavy oil or bitumen recovery solely as fuel for required energy for recovery with the recovered heavy oil or bitumen being then pipelined for upgrading to synthetic oil in refineries at the source of coal in the same overall pipeline system. The location of synthetic oil refineries at the site of large coal reserves in lower temperature climates in central southwestern Canada to avoid the cost penalties of more rigorous northern climates is of considerable interest to the invented process.
In the invented process, a preferred feedstock for hydrogen upgrading marries coal, and the volatiles from coal, with heavy oil or heavy oil bottoms remaining after initial distillation of heavy oil and upgrades that feedstock to provide a base material for producing a light synthetic crude well matched with natural crude oils on which refinery production and capacity has been based in the past. The invented process not only exploits the lower cost of coal as a basic feedstock constituent, but exploits a chemical synergy promoted by the coal constituent during hydrogen addition upgrading which promotes a high yield conversion of the coal--coal volatile--heavy oil feedstock to a higher quality light synthetic crude than may be produced from either feedstock constituent separately and at less severe operating conditions than those that would be required to upgrade either separately. The heavy oil constituent is product derived from a non-coal source. Molecular theory indicates that the highly reactive hydrogen double-bonded benzene ring molecules in the coal volatiles and crushed coal enhances recovery rates in the upgrading of the mixed feedstock. Accordingly, not only is oil recovered from coal by two means and from heavy oil, with residuals being used for energy generation, but the use of coal volatiles and crushed coal in the feedstock creates a synergistic effect on the recovery rate.
By then mixing the upgraded lighter crude oil recovered from upgrading the coal--coal volatile--heavy oil feedstock with light ends obtained from other heavy oil dedicated upgrading processes, such as distillation, a blended synthetic light crude product can be produced which has viscosity properties and benzenoid, paraffinic, napthenic and sulphur proportions comparable to that found in the better natural light crude oils.
Canadian Pat. No. 1,065,780 deals briefly with an alternative for upgrading heavy oil wherein crushed coal or shale is mixed with recovered heavy oil as the hydrocarbon feedstock to an upgrading process. This relates solely to a liquefication of oil from coal or shale, without utilizing coal and pyrolyzed coal volatiles in a proportion that would produce the chemical synergy of the present invention to significantly enhance yield and produce a base synthetic crude oil that can be used to give a synthetic crude oil compatible with present light crude oils. In addition, various levels of technology have been developed in the past for the distillation or liquefication of coal and the hydrogenation of the condensible coal volatiles (U.S. Pat. No. 3,107,985 to Huntington) and to the pyrolysis of coal and recovery of the volatile hydrocarbons (U.S. Pat. Nos. 4,085,030; 4,102,773; and 4,145,274 to Green; 2,634,286 to Elliot; 3,988,237 to Davis; and 4,229,185 to Sass). However, these are each dedicated to coal as a single source of refineable oil whereas the present invention utilizes coal and pyrolyzed coal volatiles together with heavy oil in selected proportions to produce enhanced yields of refinable (lighter) oil and to lead to the production of a lighter crude oil similar to those obtained from natural deposits.
Accordingly, a process is provided for the production of a synthetic crude oil from heavy residual non-coal material and coal in which crushed coal is thermally pyrolyzed to produce coal volatiles. The coal volatiles are condensed out and mixed with crushed coal and a heavy residual of heavy oil, tar sands bitumen or oil shale kerogens to produce a coal--coal volatile--heavy residual feedstock which is upgraded in a synergistic production of a light crude oil. The lighter crude produced can then be further mixed with light ends obtained, for example, from the distillation of heavy oil, tar sands bitumen or oil shale kerogens to produce a blended synthetic-like crude oil with a composition similar to that of natural-like crudes, a result not achieved at present by conventional independent processing of coal or heavy oils. In addition, an improved pyrolyzation apparatus for achieving the pyrolyzation of coal in the process is provided for.
In the process, the upgrader can comprise high level hydrogen additional upgrading, or alternatively, an upgrading process arrangement may be utilized whereby the hydrogen additional upgrading reactor is operated at lower severity, i.e. reduced temperature, pressure, hydrogen or catalyst consumption and/or reduced feed stock residence time, thereby providing for a lower rate of conversion of the three part feedstock mix to light oil product than is possible by higher severity operations. An increase in heavy residual materials will be produced by such lower severity hydrogen addition upgrading. The upgrading residual material is then thermally cracked into a light oil fraction and coke residuals, with a final blended light synthetic oil product comprising, for example, the light ends of the distillation of heavy liquid oil, the light products of hydrogen addition upgrading of the three part feedstock mix and the light product produced by hydrocracking the residuals from the hydrogen addition upgrading step.
After either of these upgrading methods, the combustible char residual from the coal pyrolysis step and the heavy residuals or coking residuals produced in the upgrading, as the case may be, are gasified to provide the energy for process use, including thermal energy for pyrolysis and upgrading, and as a means to hydrogen production. Alternatively, or additionally, low volatile content coal can be used as gasifier feed.
By adjustments in the proportions of each component in the three part feedstock mixture, variations may be made in the product characteristics to meet specific requirements of refineries producing different end products.
Energy is produced in-process from waste residuals of the process. The integration of processing with several systems for energy generation and production enables the process to be adjusted or tuned to different production requirements or energy requirements in different parts of the process, or to produce energy, such as electricity, as a by-product.
In addition, the process is also environmentally advantageous in that injurious emissions to atmosphere are avoided and solid wastes are minimized and readily disposed of. Where the process is located at or near the source of coal, waste materials will occupy a small fraction of coal mined-out space.